As millions of americans at airports face those long security lines we have news tonight about the threats that make those checks so critical. Four men from southern california are under arrest charged with plotting to join al qaeda and kill americans. Abc's senior justice correspondent pierre justice covers it for us a. Reporter: U.S. Law enforcement will be on the hunt. And today the fbi provided a wake-up call that there may be red cals among us. Anwar al awlaki was the world's most wanted man, public enemy number one encouraging radicals to attack america in his online preaching. The u.S. Killed him in 2011 but today we learn he is still helping to recruit terrorists from the grave. Overnight the fbi announced charges against four californian men accused of plotting to go to afghanistan to bomb and kill u.S. Soldiers. They were disciples of awlaki. There was admiration for him and quite frankly idolizing him. Reporter: The alleged ringleader, sohiel kabir was an alleged member of the air force. They went to shooting ranges and bought tickets to travel to afghanistan through mexico. This was a violent extremist network. Reporter: According to the fbi's charges one of the alleged terror cell's members posted violent extremist media including audio files of awlaki. They discovered 30 cases brought against so-called homegrown radicals where he was a primary inspiration and include recent plots to blow up the u.S. Capitol building, the federal reserve in new york and another to detonate a car bomb at a chicago bar. All the cases came after awlaki was dead. George, some officials fear we may see his influence for years to come. He lives on online. Even from the grave.

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